Abstract: Grid is a utility or infra-structure for complex, enormous computations, where remote resources are accessible through the web (internet), from desktop, laptop, mobile phone. It is similar to power grid, where the user does not have to worry about the source of the computing power. Grid can be thought of as aggregation of millions of discrete computers owned by individuals, institutes from various countries across the world connected to form a single, huge, super-computer! Undoubtedly it is an evolution of internet facility, but such aggregation of networked computer resources in dynamic and multi-institutional environment demand for higher security. This paper deals with the challenging security issues that demand new technical approaches. We describe how these issues can be resolved.